The present invention relates to internal combustion engines and more particularly to crankshafts associated with such engines.
Repeated starting and stopping of an internal combustion engine results in substantial wear of crankshaft journals and journal bearings because the engine is not properly lubricated when rotation of the crankshaft starts. Journal bearings are ordinarily designed for full hydrodynamic lubrication. In other words, the crankshaft journal and the crankshaft journal bearings usually never make contact when the engine is running because there is a hydrodynamic oil film between them that prevents metal to metal contact. However, hydrodynamic lubrication requires oil pressure and shaft rotation. Oil pressure alone does not produce hydrodynamic lubrication but only boundary lubrication. In boundary lubrication there may be metal to metal contact and wear will occur. The inventors have recognized that, to provide hydrodynamic lubrication of a crankshaft journal and bearing arrangement, there must be both oil pressure and rotation of the crankshaft.
According to an aspect of the present invention, a method of operating an engine comprises switching the engine between being fueled and in a non-fueled mode, the internal combustion engine comprising a crankshaft having a bearing journal and a bearing in which the bearing journal is rotatable, and constantly turning the crankshaft when the internal combustion engine is in the non-fueled mode.
According to another aspect of the present invention, an engine comprises an internal combustion engine comprising a crankshaft having a bearing journal and a bearing in which the bearing journal is rotatable, and means for constantly turning the crankshaft when the internal combustion engine is in a non-fueled mode.